Urea-formaldehyde compositions and their manufacture



g- 3, 1965 J. M. ODONNELL 3,198,761

UREA'FORMALDEHYDE COMPOSITIONS AND THEIR MANUFACTURE Filed April 27.1961 BASE AQUEOUS UREA (u) ACID FORMALDEHYDE (F) -24- -|3- -|7- pHGTOIOpH 3.0 T0 5.5

l-' 30 MINUTES pH 3.0 T0 5.5

TRACE LIQUID CONDENSATE CHELATING ELEMENTS CHELATING AGENT AGENT TRACEELEMENTS DRYING BY HEATING WITH ACCOMPANYING POLYMERIZATION UNDER ACIDCONDITIONS AGENT United States Patent Office 3,198,761 Patented Aug. 3,1965 3,198,761 urna-nomaarnnrrrnu CGMPGSITIONS AND TEEIR MANUFAQTUREJames M. ODonnell, North Smithfield, RL, assignor to Hercules PowderCompany, Wilmington, Del, a corporation of Delaware Filed Apr. 27, 1961,Ser. No. 106,003 9 Claims. (Ci. 26tl--29.4)

This invention relates to a method for the production of stable, liquidurea-formaldehyde condensates containing urea in a mole ratio toformaldehyde greater than 1:1 and characterized by unique film-formingproperties, and to stable, liquid urea-formaldehyde Compositions soproduced. In another aspect this invention relates to solidurea-formaldehyde fertilizer compositions containing che lating agentsand/ or trace elements, uniformly distributed, and suspended, therein,in slowly releasable form. In still another aspect, this inventionrelates to the production of the above fertilizer compositions by theformulation of a stable liquid urea-formaldehyde condensate, abovereferred to, and then incorporating in the said liquid one or both ofthe said chelating agents and trace elements followed by polymerizingthe resulting liquid admixture, under acid conditions, and drying, toproduce the solid fertilizer product. This application is acontinuation-inpart of my copending application Serial No. 609,486,filed September 12, 1956.

Urea-formaldehyde compositions in the resin and fertilizer arts containurea and formaldehyde in relative mole ratios over a broad range, forexample, from 0.1:1 to 2:1 and higher. Many processes have been proposedfor the manufacture of these compositions, each process leading to acomposition characterized by a suitable combination of urea andformaldehyde to meet the purpose at hand. In the resin art liquidurea-formaldehyde compositions contain formaldehyde in a mole ratio tourea greater than 1, the formaldehyde and urea being to a large extentchemically combined in such form as to be readily convertible toproducts such as adhesives and molding powders. These solutions providefor storage and shipping of formaldehyde and urea in form of highlyconcentrated liquids.

The fertilizer art has advantageously utilized solid urea-formaldehydecompositions containing formaldehyde in a mole ratio to urea less than 1inasmuch as these compositions provide a water-insoluble but slowlyavailable source of nitrogen for slow release during the entire growingseason. These compositions have been identified as urea-form, that termdefining the composition as the product of an acid catalyzedpolymerization or condensation of the urea and formaldehyde andcontaining urea in a mole ratio to formaldehyde greater than one andalso containing at least 35 percent nitrogen, 21 major portion of whichis in water-insoluble, but slowly available, form.

Liquid urea-form solutions, or suspensions, have met with very littleuse heretofore particularly in view of their instability over prolongedand in many instances even relatively short periods. However, as in theresin art, production of such stable solutions would constitute a markedimprovement in the art inasmuch as such liquids could be applied by anysuitable spraying technique and shipped and stored in liquid form forsubsequent incorporation with other fertilizer ingredients as needed.

The function of trace elements in the soil as plant food (i.e. minorelements suitable for plant nourishment other than nitrogen, phosphorus,potassium, calcium, magnesium and sulfur, which are major fertilizerelements) is well recognized in the art. Typical trace elements areiron, manganese, copper, zinc, boron, cobalt and molybdenum, all ofwhich have been described in the art as most agronomically useful. Insoil conditions where there is a lack of one or more of trace elements,it is, of course, imperative that they be supplied to the soil inrequisite amount. It has been proposed that trace elements beincorporated with fertilizer ingredients for that purpose. However, mostoften, the problem of water solubility is presented, the extent of whichis, of course, dependent upon the particular trace elements and the formin which they are added.

Whether the trace element occurs naturally in the soil or is added tosupplement plant feeding, it has been the practice to also include achelating agent in combination therewith. Although the role of thechelating agent is not clear at the present time, it, in combinationwith the trace elements, assists the latter in its function tofacilitate plant growth by the formation of a chelate, i.e., reaction ofthe chelating agent with the trace element to form a chelate structure;It is very likely that the effect of the chelation is, among otherfunctions, to increase water solubility of the trace element so that thelatter can be assimilated more readily by the plant.

Chelating agents often utilized heretofore, and preferred in thepractice of the invention as described hereinafter, are free aminopolycarboxylic acids and their salts with alkali, alkaline earth, andheavy metals, e.g., copper, lead, iron, nickel, cobalt, palladium,rhodium and ruthenium. Exemplary of such amino polycarboxylic compoundsare ethylene diamine tetraacetic acid (EDTA), diethylene diaminetriacetic acid, N,N'-dihydroxylethyl ethylene diamine diacetic acid,diethylene triamine pentaacetic acid (DTPA),.N-hydroxyethyl ethylenediamine triacetic acid, and alkali metal, alkaline earth and heavy metalsalts thereof. Exemplary of typical chelates derived from alkaline earthand heavy metal salts of amino polycarboxylic acids are ferric disodiumethyl ene diamine tetraacetic acid (FeNa EDTA), monosodium ferrousN-hydroxyl ethylene diamine triacetic acid (NaFe HE EDTA), magnesiumdisodium ethylene diamine tetraacetic acid (MgNa EDTA), disodiumethylene diamine tetraacetic acid, and the like.

The term EDTA compounds is used herein to refer to those chelatingagents, preferred in the practice of the invention, i.e., ethylenediamine tetraacetic acid and salts thereof. The term EDTA type compoundis used herein to typify the preferred acids and salts of ethylenediamine tetraacetic acid.

Exemplary US. patents illustrative of the arts understanding of the roleof chelating agents in combination with trace elements in the soil andtechniques for adding them to the soil, particularly as fertilizercomposition ingredients are: Bersworth, US. 2,407,645; Riddle, US.2,280,451; Vana, US. 2,732,290 and ODonnell, US. 2,882,141.

The Vana patent describes the simple admixture of synthetic fused traceelement mixtures using urea-form type fertilizers, and the ODonnellpatent discloses generally the addition of amino polycarboxylic acidcompounds to urea-forms. However, a three-component fertilizer systemcontaining urea-form and amino polycarboxylic acid compound (chelatingagent) and trace elements, as a physical mixture, is disadvantageous inthat segregation of the particles occurs within the mixture due to theextremely fine particle size of the trace element compound and of thechelting agent so that these latter compounds become more readilyavailable for plant consumption than the other fertilizer ingredients.Such overall combination product (physical mixture) also contains thechelating agent and other water-soluble compounds in readilywater-leachable form.

Thus, a key problem in the art has been that of developing a urea-form,and process for its manufacture, suitable for incorporation therewith ofchelating agents Z and trace element ingredients in the requisiteproportions and which will be uniformly dispersed throughout thecomposition and slowly released to the soil along with the majorfertilizer ingredients.

This invention is concerned with the production of liquidurea-formaldehyde condensates which contain urea in a mole ratio toformaldehyde in excess of one and which are stable over prolongedperiods and can be further reacted with urea or formaldehyde to producefinished fertilizers or resins as the case may be; and with themanufacture of slow-release type urea-form fertilizers containingchelating agents alone or with trace elements which are uniformlydispersed in the fertilizer and slowly releasable with the nitrogen. Theinvention is further concerned with compositions so produced.

It is an object of the invention to provide highly stable liquidurea-formaldehyde condensates containing urea in a mole ratio toformaldehyde greater than 1 and which can be stored over prolongedperiods and then further reacted with urea or formaldehyde to form thedesired urea-formaldehyde end product. It is another object to provide aurea-form fertilizer composition containing urea in a mole ratio toformaldehyde greater than 1 and a chelating agent alone or together withone or more trace elements uniformly distributed therein for slow release to the soil with the nitrogen. Another object is to provide aprocess for the production of the above described stable liquidurea-forrnaldehyde condensates. Another object is to provide a processfor the manufac ture of urea-form fertilizer compositions containingchelating agents alone or together with trace elements, of the kindabove described. Other objects and aspects will be apparent in light ofthe accompanying disclosure and the appended claims.

In accordance with the invention a stable liquid ureaformaldehydecondensate, containing urea in a mole ratio to formaldehyde greater than1, is produced by dissolving urea in aqueous formaldehyde in a moleratio of urea to formaldehyde within the range of from 0.31:1 to 06:1;maintaining the resulting urea-formaldehyde solution at a temperature offrom 50 to 100 C. and at a pH of from 7.0 to 10.0 for a period of from 5to 60 minutes; thereafter regulating the said pH to a value within therange of from 2.5 to 5.0 and maintaining the resulting reaction mixtureat a temperature of 40 to 100 C. for a period of from minutes to 2hours, whereby a liquid methylol urea-containing reaction product isformed; adding urea to the resulting methylol urea-containing reactionmixture in an amount sur'iicient to provide a mole ratio of total addedurea to formaldehyde therein in the range of from 1:1 to 2:1 and thenheating the resulting admixture at its existing pH, generally from a pHof 3.0 to 5.5, for a period of from 1 to 30 minutes at a temperature inthe range of from 35 to 80 C. to form said condensate; and recoveringsaid condensate as product of the process. Neutralization of the saidcondensate product to an alkaline pH of 7 to 9 is usually necessary formaximum stability. 7

Further in accordance with the invention, liquid condensate productabove described is incorporated with a substantial amount of an aminopolycarboxylic acid compound as a cheltating agent, and also, whendesired, with one or more trace elements suitable for plant nourishment,followed by polymerizing and drying the resulting liquid mixture underacid conditions to provide residual solids as fertilizer product of theinvention, the said fartilizer product being of the urea-form type andcontaining a chelating agent and trace elements, when the latter isdesired, both uniformly dispersed in the fertilizer and slowly yieldableto the soil along with the nitrogen, as free chelating agent, free traceelement or chelate (chelated trace element). Still further in accordancewith the invention, condensate product above described is further heatedat an acid pH under suitable timetemperature conditions for effectingpolymerization and drying of the liquid to provide a solid urea-formfertilizer product. The longer the time of heating, the lower is thetemperature required in carrying out the drying-polymerization step. Forexample, suitable polymerization and drying can be obtained at 50 to 150C. within a period of from 10 minutes to 16 hours whereas the samedegree of polymerization and drying can be obtained at a lowertemperature over a longer period, say at from 20 to 50 C. for a periodof from 1 to 10 days.

It is to be recognized that the conventional preparation of urea-formcompounds involves a simple combination of urea and formaldehyde in amole ratio of added urea to formaldehyde within the range of 1.2:1 toabout 1.5:1 or higher followed by acidification to form a resultingsolid polymer which is then neutralized for final stability and use.These materials, i.e., after acid polymerization, are generally obtainedas finely divided solids from a dilute solution or as a solid mass froma concentrated solution.

The present invention, on the other hand, proceeds through a preliminarypolymethylol urea stage in the formation of a stable liquidintermediate, partially condensed product, containing from about 20 to40 weight percent water, and having exceptional film-forming pro pertieson drying. The stable liquid product has the ability to incorporateadded materials such as chelating agents alone, or together with traceelements, to form chelates, into the film structure as it is formed.Upon polymerization under acid conditions and drying, a solid film-likeproduct with the properties of a urea-form fertilizer is obtained.Furthermore, in contrast to the addition of chelating agent alone orwith trace elements, to a solid urea-form, or to a urea-formaldehydebefore condensation, the added materials in the practice of theinvention are so incorporated into the structure of the solid productobtained as to be sufiiciently insolubilized but to be releasable to thesoil at a desirably slow rate.

The liquid condensate of the invention is, therefore, particularlyadapted for in situ addition of trace elements and chelating agents sothat upon polymerization and drying with concomitant formation ofpolymer film product, the trace element and chelating agent ingredients,dispersed uniformly throughout the mixture, are rigidly supported intheir initially dispersed position throughout the polymer and releasedto the soil in their free form or as chelated trace elements, with thenitrogen, at a desirably slow rate.

In the preferred practice of the invention, urea is dissolved in theaqueous formaldehyde in a mole ratio .to formaldehyde within the rangeof from 0.35:1 to 0.45:1; the resulting urea-formaldehyde solution ismaintained at a temperature of from 60 to C. at a pH of from 8.5 to 9.5for from 20 to 30 minutes; the said pH is then regulated to a value offrom 3 to 4 and the resulting reaction mixture is heated at 70 to C. for15 to 30 minutes; urea is then added in an amount to provide an overallmole ratio of added urea to added formaldehyde of from 1.2:1 to i.5 :1with accompanying temperature drop to about 40 to 45 C. and resulting pHof from about 3.3 to 4.5; and the resulting reaction mixture is heatedat40 to 60 C. for 5 to 15 minutes to provide the liquid productcondensate. When neutralizing the said product for stability purposesthe pH is adjusted .to a value of from 8.0 to 8.5. The said productcondensate generally contains from 25 to 30 percent water. Asillustrated with reference to Example IV, neutralization of the liquidproduct, for stabilization purposes, can be dispensed with when it is tobe directly utilized, i.e., without first being passed to storage.

The invention is further illustrated with reference to the block diagramof the attached drawing. Thus, formaldehyde 11 adjusted to a pH of from6 to 10, generally by the addition of sodium hydroxide or potassiumhydroxide, is admixed with urea 13 in relative proportions .to provide aresulting admixture 15 containing urea in a mole ratio to formaldehydeof from 0.321 to 0.6: 1, often about 0.35:1 to 0.45:1, the pH ofadmixture 15 being adjusted by base 24, for example, aqueous sodiumhydroxide, to a value in the order of about 7 to 10, more often about8.5 to 9.5. Admixture 15 is heated at about 50 to 100 C. for 5 to 60minutes, and then admixed with a suitable acid 17, for example,phosphoric acid, to provide acidified reaction mixture 19 at a pH offrom about 2.5 to 5.0. Reaction mixture 19 is then heated at, about 40to 100 C., for a period up to about two hours, more often from about 10to 60 minutes and more preferably for about to 30 minutes.

Additional urea 13 is then added to the acid mixture 19 to form mixture21, the amount of urea added being such as to adjust the overall moleratio of added urea to formaldehyde to a value in the range of fromabout 1:1 to 2:1, more often 1.2:1 to 1.5:1, the temperature of mixture21 decreasing during this time to say, a value in the order of about 30to 50 C. due to the negative heat of solution of the urea, and the pHincreasing somewhat to a value of from about 3.0 to about 5.5. Mixture21 is then, as mixture 23, further heated at a temperature in the rangeof about 35 to 80 C. for a period of from about 1 to 30 minutes, theabove preferred temperature and time conditions therefor being moreoften utilized. Mixture 23 is then neutralized with an additionalportion of base 24 to provide a free flowing liquid 25 at a pH of fromabout 7 to 9, more often 8.0 to 8.5, the said liquid being characterizedby a viscosity generally ranging from about 50 to 500 c.p.s. (Brookfieldviscometer) and a water content of from about to about 40 percent, moreoften about to percent, the said water content being based on totaldried weight of solids in mixture 25.

Product 25 can be dried to form a thin film of polymer having a nitrogencontent in the order of about 37 percent, a water insoluble nitrogencontent in the order of about 22 percent and an A1. value (describedhereinafter) of about 80. Preferably, however, in the event that product25' is to be converted directly to a urea-form type composition, it isfirst acidified to a pH in the range of from about 2.5 to 5.5 and driedby heating at a temperature in the order of from about 70 to 90 C. forabout .5 to 5.0 hours under which conditions polymerization of thecondensate takes place to form a solid urea-form type product having aWater insoluble nitrogen content in the order of about 60 to 70 percentand an A.-I. value in the order of about to 55.

However, in the manufacture of a three-component fertilizer composition,in the practice of one form of the invention, condensate product 25 isadmixed with from about 2 to weight percent of trace element material 27and with from about 2 to 20 weight percent of a chelating agent,generally an amino carboxylic acid compound 29 to form a liquidthree-component fertilizer mixture 31, both percentages being based onthe total solids content of mixture 25. The resulting liquidthreecomponent mixture is then dried as mixture 33 by heating at say, 70to 90 C. at a pH of from about 2.5 to 5.5 for about one hour, generallyfrom about 0.5 to 5 hours, under which conditions polymerizationproceeds to form a resulting urea-form type fertilizer containing traceelements and chelating agent uniformly dispersed therein and only slowlyavailable to the soil with the nitrogen, the resulting three componentcomposition being characterized by an insoluble nitrogen content in theorder of about 60 to 70 percent and an Al. factor in the order of about40 to 55.

However, only a chelating agent need be added during the preparation ofthe fertilizer composition 31, i.e., to yield a three-componentfertilizer composition 31' (not shown) in those instances wherein thesoil contains a sufficient amount of trace elements. In that. event,addition of trace element material 27 can be dispensed with withoutrequiring that the subsequent heating procedure, to

EXAMPLE I To 300 pounds of a 37 percent solution 1 of formaldehyde wasadded 60 pounds of urea, resulting in a mole ratio of urea-formaldehydeof 0.5 :1. The pH was adjusted to 7.5 with caustic soda and thetemperature was brought up to C. The pH of this mixture was then reducedto 3.0 and 5 percent sucrose derived from a corn extraction was added tothe mix at this point.

The entire mix was held at reflux for about one hour at which time itwas neutralized with triethanolamine and the temperature reduced to 60C. At this point enough urea was added to adjust the final formula to aU/F mole ratio of 1.36:1 and negative heat of the solution lowered thetemperature to 30 C. The entire mixture was acidified to a pH of 3.0with hydrochloric acid.

'An exothermic reaction occurred which raised the temperature to 60 C.The viscosity of the slurry increased to about 400 cps. at which timegaseous ammonia was introduced to the system in order to neutralize andcheck the reaction. At this point 18 pounds of disodiumethylenediaminetetraacetate was added to the slurry mix as well as 80pounds of trace element mix IM defined elsewhere herein. The mixture wasagitated vigorously to insure an even distribution of all particles andthe material was then placed in trays and dried under vacuum to removeall excessive moisture. A brittle, glassy urea-formaldehyde film was theresult of the preparation which was ground to a minus 20 mesh size. Thetotal nitrogen content was 37 percent; A.I. value 52.

EXAMPLE II pounds of Ferro FTE for the trace element mix IM.

Ferro FTE Extraction results on trace element trits 1 pH Fe Mn Cu Zn BTrace Element Mix 1M Analysis of trace element mix 1M 2 Copper 2. 62Manganese a 7. 86 Zinc 5. 24 Iron- 11. 53 Titanium 1. 57 Boron. 2. 62Barium 2. 62 Strontium 1. 31' Lead 1. 31 Molybdenum 26 Cobalt 06 Nickel06 Vanadium" 06 1 Obtained from Form Corporation, Cleveland,

1 Aqueous.

EXAMPLE n1 7 Richmond Hill plantation is situated in the Ogeechee Riverbasin about 14 miles south of Savannah, Georgia. This plantation foryears has been known as one of the 8 25 lbs/acre fritted trace elementsFerro FTE (8) 80 lbs/acre urea 15 lbs/acre Na EDTA 25 lbs/acre traceelement mix IM (9) 80 lbs/acre urea best lettuce producing farms in thesoutheast. The entire plantation consists of about 2000 acres devoted todiversi- 3 gs'fg fluted trace elements Fem) FTE fied truck farming andprincipally the raising of iceberg acre urea 1ettuce 25 lbs./ acre traceelement mix IM The heaviest producing area of this farm is a section(11) check Plot known as Cherry Hill Marsh, consisting of about 300 (12)110 lbs/acre urea-form Na 5 percent, 1:36 (see acres of heavy almostmuck soil created by dredging and Example dyking the Ogeechee River. Forten or fifteen years 251bS/acre FTE EXaIIIPIe YIELD 'DATA Crates/AcreGrading Expggiment 1st pick 2nd pick 3rd pick Total 3 4 0 Totgl Tonsl(SIG:

1 Includes rejects and outside leaves. 2 Rather severe toxic signsduring early growth.

Cherry Hill Marsh produced lettuce of outstanding quality and grade.

For the past four or five years, however, yield and quality showedsteady decline in spite of sound agricultural practices.

Experiments involving the use of urea-form, EDTA compounds, and traceelement mixtures were conducted, and the 300 acres has been subjected tovarious types of treatment involving 150 separate experiments.

For the purpose of demonstrating the effects of controlled EDTA compoundapplication, urea-form and trace element availability, 12 experimentsare shown and compared: In the following, the results for plot 6correspond to the composition of Example I and the results of plot 12correspond to the composition of Example 11.

Urea-form-urea-formaldehyde polymer produced in accordance with ExampleI.

Urea-form Fe, 5 percenturea-form to which has been added 5 percentferric disodium ethylene diamine tetraacetic acid.

Urea-form Na 5 percenturea-form to which has been added 5 percentdisodium ethylene diamine tetraacetic acid.

(1) 100 lbs/acre urea-form, 1:36 mole ratio, activity index 52 (2) 120lbs./ acre urea-form Fe, 15 percent, 1:36 U/F mole ratio, activity index50 (3) 120 lbs/acre urea-form Fe, 5 percent, 1:36 U/F mole ratio,activity index 55 (4) 110 lbs/acre urea-form Na 1:36 U/F mole ratio,

activity index 52 (5) 110 lbs/acre urea-form Na 15 percent, 1:36 moleratio 25 lbs/acre trace element mix IM (6) 110 lbs/acre urea-form Na 5percent, 1:36 U/F mole ratio 25 lbs/acre trace element mix IM (seeExample I) (7) 80 lbs/acre urea 15 lbs./ acre Na EDTA The experiments onlettuce production showed in some cases almost a 100 percent increase inyield and far more than 100 percent increase in better grading.Experiments 5, 6 and 12 illustrate the preferred three-componentcompositions of the present invention. 7

Experiment 6 used compositions from procedure of Example I andExperiment 12 used compositions from the procedure of Example 11.Experiments 5, 6 and 12 showed unique superiority over analogous one andtwocomponent systems shown in Experiments 1 to 4 inclusive. Experiments5, 6 and 12 additionally showed unique superiority over analogous twoand three-component systems of unresinified urea shown in Experiments 7to 11.

The amount of amino polycarboxylic acid compound and the amount of traceelement mixture most advantageously present in the solidurea-formaldehyde (ureaform) polymer from the plant food standpoint is,of course, contingent largely on rate of release required in adetermined amount of time, rate of growth stimulant 3 or trace elementapplication desired per given area, frequency and extent of solubilizingfactors such as rainfall, soil condition, and the extent to whichnitrogen in a slowly available form was desired. However, contents offrom 2 to 50 percent trace element mixture and from about 2 to 20percent amino polycarboxylic acid compound are generally adequate andare readily incorporated into the urea-form in accordance with theinvention.

EXAMPLE IV Thirty-seven percent aqueous formaldehyde (200 g.) wasadjusted to a pH of 7.0 using dilute sodium hydroxide solution. Urea (65g.) was then added to the formaldehyde to give a urea-formaldehyde moleratio of 0.42:1, and the mixture 'was heated at 45 C. over a 5-minuteperiod to form a clear solution. The pH of the solution was thenadjusted from 7.3 to 9.4 using 50% NaOH and the resulting solution washeated for 25 minutes at 90 C. The still-clear solution was cooled to C.and the pH was adjusted from 7.6 to 3.5 using 42% H PO It was thenheated for 20 minutes at 80 C., during which time it remained clear.Additional urea (126 g.) was then added to give a finalurea-formaldehyde mole ratio of 1.3:1. Addition of the urea caused thetemperature to drop to 45 C. The mixture was stirred for 3 minutes at 45C. The resulting reaction mixture, a solution, was now cloudy and had apH of 4.3, and constituted a liquid condensate product of the invention,referred to hereinafter as Product A.

A portion (100 g.) of the above liquid condensate Product A was removedfrom the said reaction mixture and was poured directly into a dish toform a in. layer and allowed to stand at 20-25 C. After 24 hours thefilm was quite hard and brittle. After 56 hours the film was ground in amortar and the particles were screened to recover material passing alit-mesh screen and retained on 30 mesh.

In the preparation of a chelating agent to be utilized as describedhereinafter a disodium salt of ethylene diamine tetraacetate (11.2grams) was dissolved in 50 ml. of hot water. To this was added a hotsolution of an equimolar amount (11.8 g.) of ferrous ammonium sulfate in50ml. of water. The resulting thick paste was filtered and washed with10 ml. or" water. After air drying, the yellow-brown solid iron-saltcomplex so produced was ground to a fine powder.

A second portion (100 g.) of the same liquid condensate was removed fromthe reaction mixture and directly mixed thoroughly with 3.5 g. of theiron complex described above, and a film was cast, air dried, ground,and screened in a manner identical with that described above. On a drybasis this material contained 5 percent of the iron complex and isdesignated herein as Prodnot B.

Two glass tubes mm. 1.1).), each closed with glass wool at the bottom,were filled with the screened dried products to form two columns about12 in. high. One column was packed with g. of the material containing 5percent of the iron complex, i.e., Product B. The other column waspacked with a thoroughly blended, mechanical mixture of 19 g. ofscreened Product A plus 1.0 g. of the iron complex prepared as abovedescribed to pro- Vide a mechanical mixture containing 5 percent of theiron complex. Room temperature (2025 C.) water was then allow-ed todrain through each of these columns and then collected. The followingtable summarizes the observations made.

The pH of a third portion of the liquid ProductA was adjusted to 8.5utilizing 20 percent aqueous sodium hydroxide. The resulting product wasfree flowing and contained no appreciable amount of sediment materialafter 40 days storage at ambient room temperature.

EXAMPLE V Thirty-seven percent aqueous formaldehyde (200 g.) wasadjusted to pH 7.0 using 20 percent NaOH solution. Urea (65 g.) wasadded to the formaldehyde to give a urea-formaldehyde mole ratio of0.44:1 and the mixture was heated at C. for 5 minutes to dissolve theurea. The pH of the solution was then adjusted from 7.2 to 9.4 usingpercent NaOI-I and the solution was heated for 25 minutes at 80 C.. Thestill clear solution was adjusted to pH 3.5 using 42 percent H PO Thesolution was then heated for 35 minutes at 80 C. during which time itremained clear. Additional urea (126 g.) was then added to give a finalU/F mole ratio of 1.3. Addi:

tion of the urea caused the temperature to drop to 45 C.

The mixture was stirred at 45 C. for 10 minutes, the pH now being 4.0.The pH of the resulting liquid product condensate was then adjusted to8.5 with 20 percent NaOH solution. The said product was an opaquesolution and was free flowing and contained no appreciable amount ofsediment material after 36 days storage at ambient room temperature.

A portion of this solution (100 g.) (U/F condensate of the invention)was adjusted to pH 3.5 using 42 percent H PO and then poured out into athin layer and allowed to react at 80 C. for 2 hours. The resultanturea-form product had an A.I. of 55, with 23 percent WIN (cold waterinsoluble nitrogen).

percent, remainder inerts) finely ground mixed fertilizer was mixed in alaboratory granulator with 300 g. 16' mesh vermiculite. To this wasadded 100 ml. water. Three hundred g. of the product condensate preparedas in Example V was then added. When satisfactory granulation wasachieved (10 to 15 min.) the product was dried in a rotary drum drierfor 1.0 hour at 80 to 100 C. Aided by the acidity inherent in the 51010fertilizer (the aqueous slurry had a pH of 4.7), the result was a granu-Table Screened Sample B Screened Sample A plus 5 percent ComplexLeaching Sample Leaching Iron in Color of Leaching Leaching Iron n Colorof Leaching Water Leaching Water Water Leaching ater (ml.) Water (g.)(ml.) Water (g.)

25 0. 0052 Very yellow 25 O. 0460 Yellow-brown. 25 d 25 0. 0029 Verylight yellow. 25 25 0. 0004 Colorless. 25 25 0.0001 D0. 25 25 0.0002 D0.25 25 0. 0001 D0. 50 50 0. 0014 Very light yellow- 50 0. 0012 Almostcolorless-.-"

Example 1V further demonstrates that the rate of leaching is many timeslower in the case of the screened sample B than in the case of thescreened sample A mechanically mixed with the iron complex. This isfurther exemplary of the unique film-forming properties of the liquidU/F condensate products of the invention and the manner by which thechelating agent and trace elements are held in the polymerized and driedcondensate in uniformly dispersed suspension for slow release with thenitrogen to the soil.

lated mixed fertilizer containing urea-form having an A.I. of 55.EXAMPLE VII Forty-three grams of product condensate prepared as inExample V was adjusted to pH 4.5 using 20 percent H PO and thoroughlymixed with 20 g. No. 4 vermiculite. The product was dried for 16 hoursat 50 C. The urea-form made had an A.I. of 56 and 58 percent of thetotal nitrogen was cold water insoluble.

1 1 EXAMPLE VIH One hundred grams of the condensate product prepared asin Example V and 65 g. 46 percent aqueous formaldehyde were mixed andthe pH of the solution was adjusted 12 HWIN=hot water (99 C. to 100 C.)insoluble nitrogen in phosphate butter solution As will evident to thoseskilled in the art, various modifications can be made or followed, inthe light of to pH 8.5. The solution was refluxed for 15 minutes and 5the foregoing disclosure and discussion, without departcooled to 85 C.The pH was adjusted to 3.5 and the ing from the spirit or scope of thedisclosure or from the solution was refluxed until the viscosity at 25C. increased scope of the claim. from 24 c.p.s. to 1100 c.p.s. Thisviscosity change is typi What I claim and desire to protect by LettersPatent is: cal of resin formation from urea and formaldehyde. The 1. Aprocess for producing a stable liquid urea-formresin product containedformaldehyde in a mole ratio to aldehyde condensate containing urea in amole ratio to urea of 1.8: l. formaldehyde greater than 1, andcharacterized by film- The stability of the liquid product condensate ata pH forming properties, which comprises admixing urea with of about 7or higher of the invention is such that it is free aqueous formaldehydein a mole ratio of urea to formflowing and free from any appreciableamounts of sedialdehyde within the range of from 0.321 to 06:1 underment after periods of at least 20 days and up to about 55 temperatureconditions for dissolving the urea in the said days. aqueousformaldehyde; maintaining the resulting urea- EXAMPLE 1X formaldehydesolution, as a reaction mixture, at a tem- The following tabulationillustrates stability character- Perature of from 50 t0 alld a P of fromistics of several liquid product condensates, each prepared 7 t0 for aPerlod of 9 5 t0 6O i thereafter in accordance with the processillustrated with reference Iedllcmg the P Of t e nd reactlon mixture toa value to ExamplesIVandVhereinabove. within the range of from 2.5 to5.0 and maintaining Alkaline Treatment Acid Treatment min.)

Product Stability Before Urea Add After Urea Add at 25 0. H T ellp.U/lfi y p (m0 6) Temp. Time Temp. Time U/F pH 0.) (min.) pH 0.) (min)(mole) 10.0 90 o. 44 3. 5 so 20 3. 5 70 10 1.30 3. 0 70 o. 44 3. 5 so 203. 5 10 1. 42 3o 8. 0 7o 0. 5o 3. 5 80 20 3. 5 45 20 1. 42 3o 9. 4 7o 0.44 3. 5 so 20 3. 5 45 2 1.30 25 9. 4 70 0. 44 a. 5 9o 10 3. 5 45 2 1. 2925 9. 0 90 0. 5 3. 5 30 2o 3. 5 45 10 1. 40 9. 4 0. 5 3. 5 so 20 3. 5 5010 1. 40 2s 1 The number of days observed to be free flowing and free ofany appreciable amount of sediment. pH of each sample tested wasadjusted to the alkaline side at the time the sample was taken from theprocess for storage.

Although when referringherein to trace element mix- 40 tures, it ismeant a mixture which, as illustrated, contains one or more traceelements suitable for nourishment of the soil, it is also intended toinclude single trace element materials such as, for example, ironsulfate or other suitable compounds which supply but a single traceelement.

Although the invention contemplatesv generally, trace elements oflimited water solubility, those characterized by higher solubility,e.g., iron sulfate above mentioned, are also within the scope of theinvention. It is in any event, the concept of controlling the rate ofrelease of the trace element (or chelating agent or both) to the soilthat is basic to the fertilizer compositions of the invention; and thatis in turn determined by dispersion and suspension of the material inthe solid slowly water soluble ureaform film.

By the expression A.I. value referred to herein is meant activity indexwhich test measures the percent of cold water insoluble nitrogen thatdissolves in a hot bufi'ered phosphate solution. The Al. test hasfurther acceptance in the fertilizer industry and is referred to in thefollowing publications:

Report of the Subcommittee Recommendations of the I Referee-NitrogenActivity Index, Smith, J. F.

J.A.O.A.C. 38, No. 1, page 64 (1955), and Official PublicationA.A.F.C.O. No. 8 (1954), page 14, (N-O-16 urea formaldehyde fertilizermaterials).

The Al. is calculated 7 same at a temperature within the range of from40 to 100 C. for a period of from 10 minutes to 2 hours; addingadditional urea to the resulting reaction mixture in an amountsuflicient to provide a mole ratio of total added urea to total addedformaldehyde therein greater than 1:1 but not exceeding 2:1 and thenheating same for a period of from 1 to 30 minutes at a temperaturewithin the range of from 35 to C., and recovering resulting liquidreaction mixture as said liquid urea-formaldehyde condensate.

2. In a process of claim 1 adjusting the pH of the saidurea-formaldehyde condensate product to a value on the alkaline sidewhereby the said condensate is stabilized for storage over prolongedperiods.

3. A process for producing a stable liquid urea-formaldehyde condensatecontaining urea in a mole ratio to formaldehyde greater than 1 andcharacterized by filmforming properties, which comprises admixing ureawith aqueous formaldehyde in a mole ratio of urea to formaldehyde withinthe range of from 0.35:1 to 0.45:1 under temperature conditions fordissolving the urea in the said aqueous formaldehyde; maintaining theresulting ureaformaldehyde solution, as a reaction mixture, at atemperature of from 60 to 80 C. and at a pH of from 8.5 to 9.5 for aperiod of from 20 to 30 minutes; thereafter reducing the pH of the saidreaction mixture to a value within the range of from 3 to 4 andmaintaining same at a temperature within therangeof from 70 to C. for aperiod of from 15 to 30 minutes; adding additional urea to the resultingreaction mixture in an amount sufficient to provide a mole ratio oftotal added urea to total added formaldehyde therein within the range offrom 1.221 to 1.511 and then heating same over a period of from 5 to 15minutes at a temperature of from 40 to 60 C., and recovering resultingliquid reaction mixture as said liquid urea-formaldehyde condensate.

4. A process of claim 3 wherein the pH of the said 13 resulting liquidreaction mixture is adjusted to a value on the alkaline side wherebysaid condensate is stable over proionged periods.

5. The process of claim 1 wherein the temperature Within the said rangeof from 40 to 100 C. is maintained for a period of from 5 to 60 minutesand wherein the temperature during the said period of from 1 to 35minutes is maintained Within the range of from 35 to 70 C.

6. The process of claim 5 wherein the said temperature range of from 35to 70 C. is maintained for a period of from 1 to 30 minutes.

7. A process for producing a solid polymeric ureaformaldehyde containingurea in a mole ratio to formaldehyde greater than 1, which comprisesadmixing urea With aqueous formaldehyde in a mole ratio of urea toformaldehyde within the range of from 0.311 to 0.611 under temperatureconditions for dissolving the urea in the said aqueous formaldehyde;maintaining the resulting urea-formaldehyde solution, as a reactionmixture, at a temperature of from 50 to 100 C. and at a pH of from 7 to10 for a period of from 5 to 60 minutes; thereafter reducing the pH ofthe said reaction mixture to a value within the range of from 2.5 to 5.0and maintaining same at a temperature Within the range of from 40 to 100C. for a period of from 10 minutes to 2 hours; adding additional urea tothe resulting reaction mixture in an amount suiiicient to provide a moleratio of total added urea to total added formaldehyde therein greaterthan 1:1 but not exceeding 2:1 and then heating same for a period offrom 1 to minutes at a temperature within the range of from to 80 C.,whereby a stable liquid ureaforrnaldehyde condensate is formed; furtherheating said condensate under pH conditions on the acid side for a timesufficient to effect polymerization and drying of same to form a solid;and recovering the resulting solid as product of the process.

8. A stable liquid urea-formaldehyde condensate having film-formingproperties upon drying and characterized by a Water content in the rangeof from 20 to weight 14 percent and a viscosity of from to 500 c.p.s.,prepared by admixing urea with aqueous formaldehyde in a mole ratio ofurea to formaldehyde within the range of from 0.3:1 to 0.6: 1 undertemperature conditions for dissolving the urea in the said aqueousformaldehyde; maintaining the resulting urea-formaldehyde solution, as areaction mixture, at a temperature of from 50 to 100 C. and at a pH offrom 7 to 10 for a period of from 10 minutes to 2 hours; thereafterreducing the pH of the said reaction mixture to a value within the rangeof from 2.5 to 5.0 and maintaining same at a temperature within therange of from 40 to 100 C. for a period of from 5 to minutes; addingadditional urea to the resulting reaction mixture in an amountsuflicient to provide a mole ratio of total added urea to total addedformaldehyde therein greater than 1:1 but not exceeding 2:1 and thenheating same for a period of from 1 to 30 minutes at a temperaturewithin the range of from 35 to C., whereby the resulting liquid reactionmixture is said liquid urea-formaldehyde condensate.

9. A stable liquid urea-formaldehyde condensate of claim 8 wherein thepH of the said resulting liquid reac tion mixture is adjusted to thealkaline side, whereby said condensate is stable over prolonged periods.

References Cited by the Examiner UNITED STATES PATENTS 2,652,377 9/53Kise 26069 2,729,611 1/56 Chesley et al. 260-294 2,766,283 10/56 Darden260-69 2,829,126 4/58 Suen et al 260-69 2,872,425 2/59 Paz 26029.42,936,226 5/ 60 Kaufman 71-1 2,958,594 11/60 Halpern 71--1 2,999,8479/61 Nemes et al. 26069 WILLIAM H. SHORT, Primary Examiner.

M. A. BRINDISI, Examiner.

1. A PROCESS FOR PRODUCING A STABLE LIQUID UREA-FORMALDEHYDE CONDENSATECONDENSATE CONTAINING UREA IN A MOLE RATIO TO FORMALDEHYDE GREATER THAN1, AND CHARACTERIZED BY FILMFORMING PROPERTIES, WHICH COMPRISES ADMIXINGUREA WITH AQUEOUS FORMALDEHYDE IN A MODE RATIO OF UREA TO FORMALDEHYDEWITHIN THE RANGE OF FROM 0.3:1 TO 0.6:1 UNDER TEMPERATURE CONDITIONS FORDISSOLVING THE UREA IN THE SAID AQUEOUS FORMALDEHYDE; MAINTAINING THERESULTING UREAFORMALDEHYDE SOLUTION, AS A REACTION MIXTURE, AT ATEMPERATURE OF FORM 50 TO 100*C. AND AT A PH OF FROM 7 TO 10 FOR APERIOD OF FROM 5 TO 60 MINUTES; THEREAFTER REDUCING THE PH OF THE SAIDREACTION MIXTURE TO AVALUE WITHIN THE RANGE OF FROM 2.5 TO 5.0 ANDMAINTAINING SAME AT A TEMPERATRUE WITHIN THE RANGE OF FROM 40 TO 100*C.FOR A PERIOD OF FROM 10 TO 2 HOURS; ADDING ADDITIONAL UREA TO THERESULTING REACTION MIXTURE IN AN AMOUNT SUFFICIENT TO PROVIDE A MOLERATIO OF TOTAL ADDED UREA TO TOTAL ADDED FORMALDEHYDE THEREIN GREATERTHAN 1:1 BUT NOT EXCEEDING 2:1 AND THEN HEATING SAME FOR A PERIOD OFFROM 1 TO 30 MINUTES AT A TEMPERATURE WITHIN THE RANGE OF FROM 35 TO80*C., AND RECOVERING RESULTING LIQUID REACTION MIXTURE AS SAID LIQUIDUREA-FORMALDEHYDE CONDENSATE.